A power semiconductor device for use in a power apparatus dealing with a high voltage and a large current is required to be low in power loss, large in controllable current and high in reliability. As conventional power semiconductor devices being large in controllable current and large in power capacity, an insulated gate bipolar transistor (IGBT) and a self-excited thyristor made of silicon (Si) are available. The self-excited thyristor is a thyristor capable of carrying out on/off control according to a gate control signal, and a gate turn off thyristor (GTO thyristor), a static induction thyristor, a MOS thyristor, etc. are known. In addition, as other power semiconductor devices, diodes having a pn-junction, such as a pn-junction diode, an MPS (Merged pin/Schottky) diode and an SRD (Soft and Recovery Diode), are known.
In recent years, wide-gap semiconductor materials, such as silicon carbide (SiC), are attracting attention as semiconductor materials to substitute for Si. In comparison with Si, SiC has excellent physical characteristics, being remarkably high in dielectric breakdown field strength, operable at a high temperature of 150° C. or more and large in energy gap. The development of power semiconductor devices using SiC as a material suited for power semiconductor devices which are low in loss and high in withstand voltage is carried out. As a self-excited thyristor made of a wide-gap semiconductor material, a SiC-GTO thyristor has been disclosed in 2001 IEEE ELECTRON DEVICE LETTERS, Vol. 22, No. 3, pages 127 to 129. In the SiC-GTO thyristor, the gate control signal only selects either current flowing (ON) or current shutoff (OFF) but does not control the value of the current, therefore a controllable current is larger than that of the IGBT. The switching speed of the SiC-GTO thyristor is very high, having a level equivalent to that of the Si IGBT, therefore its switching loss is as small as that of the Si IGBT.
Nonpatent literature 1: 2001 IEEE ELECTRON DEVICE LETTERS, Vol. 22, No. 3, pages 127 to 129.
Nonpatent literature 2: Proceedings of the 14th International Symposium on Power Semiconductor Devices & ICs 2002, pages 41 to 44